1. Field of the Invention
The invention relates to synchronizing a randomized video signal to a phase-locked sampling system. More specifically, the invention is directed to an apparatus and method for scrambling and descrambling video signals recorded on a videotape recorder and for correcting time-base errors undesirably present in the descrambled signal.
2. Description of the Prior Art
Certain systems for descrambling video signals (which typically have deliberately been scrambled to prevent unauthorized use thereof) introduce time base errors into the video signal. It is well known to use a device called a time-base corrector for restoring time stabilization to these descrambled signals. Typically the time-base corrector corrects the time-base errors prior to descrambling. However, a time-base corrector costs about $3,000 to $5,000 and is a relatively bulky instrument typically for professional use only and including a good deal of relatively expensive electronic memory and highly sophisticated clocking circuits. In such a time-base corrector a clock signal is created that is controlled by the position of horizontal synchronization signals in combination with the phase of the color burst in the recorded video signal. The video signal is loaded (utilizing an off-tape clock signal) either into a line memory or a field or frame memory in the time-base corrector. The time-base corrector includes a variable clock generator which tracks the time-base errors of the incoming signal and then clocks out the video signals from the memory with a fixed clock signal included. Thus, any time (i.e. phase) ambiguity or aberrations in the video signal are removed by the time-base correction process.
It would be highly desirable to provide a method for correcting time-base errors in a descrambled video signal without the need to use a time-base corrector apparatus or equivalent circuitry. Heretofor, such a method has not been available.